This invention relates to an anode for a high temperature fuel cell using hydrogen absorbing alloys or metal hydrides at least in part, or more particularly to an anode for a molten carbonate fuel cell, which is utilized in a co-generating system of low pollution and high efficiency.
In the conventional anode for a high temperature fuel cell, nickel or nickel alloy has been used in consideration of the cost, oxidation catalytic ability of hydrogen which is used as fuel, electron conductivity, and high temperature stability in reducing atmosphere.
The problems to be solved relating to such anodes for a high temperature fuel cell, especially anodes for a molten carbonate type fuel cell may be summarized into reduction of function due to decrease of the porosity and specific surface area of the anode by oversintering of the nickel which is the principal constituent material in the course of time during operation of the cell at high temperature. Since the anode is a porous gas diffusion electrode, the area of the active portion contributing to the electrode reaction is closely related with to the porosity and specific surface area of the electrode. Therefore, the oversintering of the porous anode gives rise to drop of cell performance, and also dominates the cell life, and hence it is a serious problem.
To solve the above problems, in the conventional anode for a high temperature fuel cell, nickel alloys or their mixtures with ceramics or electrolyte have been used. In particular, in the case of molten carbonate fuel cell, ceramics have been added to nickel-chromium alloy, nickel-aluminum alloy or nickel. These alloys, however, involve other problems, such as corrosion of chromium or other element in the alloy, lowering of electron conductivity or difficulty in forming the anode due to increase of content of chromium or aluminum contained in the above, or failure in prevention of oversintering if the content of chromium or aluminum is too low. Concerning the oxidation catalytic ability of hydrogen, besides, when chromium, aluminum or other is added to the nickel in order to prevent oversintering, the nickel's own catalytic ability for hydrogen oxidation is lowered.